Possibly the son of Major General Sidney Selden Long, Selden Herbert Long was commissioned in the Durham Light Infantry before he transferred to the Royal Flying Corps on 25 March 1915. 2nd Lieutenant Long received Royal Aero Club Aviator's Certificate 1046 on a Maurice Farman biplane at military school, Brooklands on 25 January 1915. He scored nine victories flying the D.H.2. Post-war, he published Into the Blue (1920) and Navigational Wireless (1927).

Great Britain, Royal Aero Club Aviators' Certificates, 1910-1950

Military Cross (MC)

2nd Lieutenant Selden Herbert Long, The Durham Light Infantry and Royal Flying Corps.
For conspicuous gallantry on several occasions,
notably the following: —
On 10th September, 1915, he went out to
attack an observation balloon shed with a
100-lb. bomb, but, being heavily fired at by an anti-aircraft battery, he silenced the guns
with this bomb and returned for another
one, with which he attacked the balloon. He only narrowly missed it as it was being
deflated beside the shed.
On 23rd September he made two determined
attacks on trains from 500 feet,
breaking the rails in two places. On the
first occasion he returned to the attack three
times, and finally climbed to 1,000 feet in
order to make better use of his bomb sight;
on the second occasion he made most of his
return journey at 1,000 feet in order better
to examine villages, roads, etc.
On 25th September he attacked a train at
500 feet under heavy rifle fire, and damaged
the line.
Late in the afternoon of 25th September
he heard that trains were moving at 25 miles
distance, and, in spite of darkness and bad
weather, he volunteered to attack them.
Heavy rain prevented his reaching them, so
he turned to attack Péronne station, descending to 500 feet and coming under heavy
anti-aircraft gun fire. This fire prevented
his reaching the station, but he climbed to
1,500 feet and attacked a "Rocket"
battery, silencing one of its guns.

Lt. (temp. Capt.) Selden Herbert Long, M.C., Durh. L.I. and R.F.C.
For great skill and daring in piloting his machine. He shot down an enemy machine, which fell in our lines, and the same day he forced another hostile machine to land in the enemy's lines. Later, he shot down another enemy machine, which fell in our lines.